Implantable electrical stimulators may be used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastroparesis. In general, an implantable stimulator delivers neurostimulation therapy in the form of electrical pulses. An implantable stimulator may deliver neurostimulation therapy via one or more leads that include electrodes located proximate to target tissues of the brain, the spinal cord, pelvic nerves, peripheral nerves, or the stomach of a patient. Hence, stimulation may be used in different therapeutic applications, such as deep brain stimulation (DBS), spinal cord stimulation (SCS), pelvic stimulation, gastric stimulation, or peripheral nerve stimulation. Stimulation also may be used for muscle stimulation, e.g., functional electrical stimulation (FES) to promote muscle movement or prevent atrophy.
Implantable medical leads carry electrodes that may be used to deliver electrical stimulation and/or sense electrical physiological signals. Different examples of implantable medical leads include cylindrical leads carrying ring electrodes or segmented electrodes and paddle style leads that carry electrode contacts. Paddle style leads may provide directional stimulation, but often require surgical implantation, although percutaneous implantation is possible. Cylindrical leads with ring or segmented electrodes may be implanted surgically or percutaneously. Ring electrodes may provide a less focused stimulation field that extends radially from the lead in many directions. Segmented electrodes may provide directional stimulation.